1. Field of the Invention
The present invention relates generally to thin film magnetic heads used to read and write data onto magnetic media, and more particularly to the use of ion milling, such as with the use of a focused ion beam (FIB) tool, to trim the pole tip lateral edges to achieve a narrow track width.
2. Description of the Prior Art
Thin film magnetic recording heads are generally utilized in the data storage industry to record data onto magnetic media, such as magnetic hard disks. It is an industry-wide goal to store ever increasing quantities of data upon the magnetic media by increasing the areal density of the data stored on the media. The areal data storage density is typically increased by increasing the linear density of the data bits (bits per inch, BPI), and/or by writing the data in narrower tracks (tracks per inch, TPI). With regard to hard disks, where the data is written in narrower circular tracks on the disk, more data tracks per inch can be written and therefore more data can be stored on the disk when the TPI is increased.
The width of the data track that is written by a recording head is generally determined by the width of the second magnetic pole, termed the P2 pole, of the write head, and efforts have been undertaken in the prior art to devise methods for reducing the width of the base of the P2 pole, commonly referred to as the P2B dimension. These prior art methods have included the use of ion beams to irradiate selected areas of the P2 pole to remove material and thereby reduce the P2B dimension.
With particular regard to the present invention, the use of a focused ion beam (FIB) to mill portions of the P2 pole to reduce the P2B dimension is known. Such prior art efforts have indeed reduced the P2B dimension, however the use of the FIB tool, particularly where the P2B dimension is quite small can be problematic. Specifically, owing to the current density distribution within the FIB tool ion beam, the edges of a milled P2 pole tip are rounded, rather than being sharp edges. The rounded edges of the P2 pole result in a P2B dimension that is unpredictable and a P2 pole that is non-optimum. There is therefore a need for an improved method for conducting the FIB milling of the write head which results in a P2 pole having sharp milled lateral edges and a clearly defined P2B dimension. Where the milled lateral edges of the P2 pole are sharp, a clearly defined track width is created and unwanted side writing from the pole tip is significantly reduced, such that narrower data tracks are produced and the data tracks can be written closer together, thus resulting in increased TPI and increased areal density of the data upon the magnetic media.